Mountain passes could see several inches of snow at snow levels as low as about 3,500 feet.
Travel on mountain roads, including the 5 Freeway, could become difficult or impossible, just as storms on Christmas and Thanksgiving proved.
A storm on Christmas Day prompted a more than 36-hour closure of the Grapevine, leaving drivers stranded with many sleeping in their vehicles overnight.
The Grapevine closed twice on Thanksgiving as heavy snow made driving conditions on the major thoroughfare treacherous.
Wind advisories are in effect in higher elevations through Friday at 4 a.m., which could create hazardous conditions, particularly for big rig drivers.
The storm system is expected to move into the area by the afternoon, with the heaviest rain and snow around 6 p.m.